| 1 | The Geochemical and Zircon Trace Elements Characteristics of A-type Granitoids in Boziguoer, Baicheng County, Xinjiang显示文摘The Boziguoer A-type granitoids in Baicheng County,Xinjiang,belong to the northern margin of the Tarim platform as well as the neighboring EW-oriented alkaline intrusive rocks.The rocks comprise an aegirine or arfvedsonite quartz alkali feldspar syenite,an aegirine or arfvedsonite alkali feldspar granite,and a biotite alkali feldspar syenite.The major rock-forming minerals are albite,K-feldspar,quartz,arfvedsonite,aegirine,and siderophyllite.The accessory minerals are mainly zircon,pyrochlore,thorite,fluorite,monazite,bastnaesite,xenotime,and astrophyllite.The chemical composition of the alkaline granitoids show that SiO2varies from 64.55%to 72.29%with a mean value of 67.32%,Na2O+K2O is high(9.85%–11.87%)with a mean of 11.14%,K2O is 2.39%–5.47%(mean=4.73%),the K2O/Na2O ratios are 0.31–0.96,Al2O3ranges from 12.58%to 15.44%,and total FeO T is between 2.35%and 5.65%.CaO,MgO,MnO,and TiO2are low.The REE content is high and the total SREE is(263–1219)ppm(mean=776 ppm),showing LREE enrichment and HREE depletion with strong negative Eu anomalies.In addition,the chondrite-normalized REE patterns of the alkaline granitoids belong to the'seagull'pattern of the right-type.The Zr content is(113–1246)ppm(mean=594 ppm),Zr+Nb+Ce+Y is between(478–2203)ppm with a mean of 1362 ppm.Furthermore,the alkaline granitoids have high HFSE(Ga,Nb,Ta,Zr,and Hf)content and low LILE(Ba,K,and Sr)content.The Nb/Ta ratio varies from 7.23 to 32.59(mean=16.59)and the Zr/Hf ratio is 16.69–58.04(mean=36.80).The zircons are depleted in LREE and enriched in HREE.The chondrite-normalized REE patterns of the zircons are of the'seagull'pattern of the left-inclined type with strong negative Eu anomaly and without a Ce anomaly.The Boziguoer A-type granitoids share similar features with A1-type granites.The average temperature of the granitic magma was estimated at 832–839°C.The Boziguoer A-type granitoids show crust–mantle mixing and may have formed in an anorogenic intraplate tectonic setting under high-temperature,anhydrous,and low oxygen fugacity conditions. | LIU Chunhua YIN Jingwu WU Cailai SHAO Xingkun YANG Haitao XU Haiming WANG Jun | 2013 | Acta Geologica Sinica(English Edition)2013，87，6： | 2 |
您所在的机构暂未开通此部分的功能，请联系管理员